Method of using ultrasonic dental tool

ABSTRACT

Method and device for fracturing the interface between dental structures that have been secured together, and for adhesive removal and cleaning of the teeth. The device comprises an ultrasonic tool for providing hi-directional movement of a preferred amplitude and frequency. The tool is applied against one of the dental structures at an acute angle with respect to a plane in which the interface between the dental structures lies. Alternatively, the dental tool is applied against the adhesive on the tooth surface for removal thereof. In another alternative, the dental tool is utilized with a liquid layer to provide cavitation of the liquid, thereby cleaning and polishing the enamel surface.

RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.07/588,281, filed Sep. 26, 1990, now U.S. Pat. No. 5,106,302, issuedApr. 21, 1992.

FIELD OF THE INVENTION

The present invention relates to a dental tool and method of use, andmore particularly, to a tool for fracturing the interface between twodental structures that have been secured together, and for cleaningteeth and removing adhesive therefrom.

BACKGROUND OF THE PRESENT INVENTION

In the dental and orthodontic field it is often necessary to break anadhesive bond that has been formed between two dental structures. Forexample, the removing of orthodontic bands or brackets from teeth at thecompletion of treatment. Typically, orthodontic brackets are removed bymechanical devices with the application of a force. These devicesgenerally comprise various types of orthodontic pliers or mechanicalarms that can be used as levers. Orthodontic bracket removinginstruments generally apply force to the interface between the bracketand the tooth that contains an appropriate orthodontic adhesive. In thesituation of typical metal orthodontic brackets, the force that isapplied deforms the orthodontic bracket which is substantially moreductile than the tooth or adhesive. Deformation of the bracket createsmicrocracks on and within the adhesive layer which ultimately results inbond failure. While such techniques have been generally accepted inremoving metal orthodontic brackets, the debonding of ceramic brackets(for example, brackets made of alumina) is not easy to accomplish. Thisis due in part to the high rigidity of the ceramic materials used toform the bracket, thus deformation of the ceramic bracket does notoccur. Therefore, the force needed to debond a ceramic bracket issubstantially greater since tensile or shear mode of failure must occuras opposed to the peeling type of removal that occurs in metal typebrackets. Additionally, ceramic brackets frequently use a chemicalbonding system which provides extremely high bond strengths. The typicalforces used to debond ceramic brackets can lead to substantial trauma tothe patient, as well as the possibility of removing enamel from thetooth, which is highly undesirable.

Several methods have been suggested in the prior art in order tominimize enamel damage and patient trauma during debonding of suchbrackets. One such method includes the application of heat to soften theadhesive. An example of this is illustrated in U.S. Pat. No. 4,907,965.Another method is a thorough cleaning of the bracket base periphery bydental burrs prior to debonding. Yet a third method requires use of alever arm for applying a torsional load to the bracket. However, none ofthese proposed methods have been successful in either reducing patienttrauma and/or reducing the possibility of enamel damage.

There has also been suggested in the prior art the removing oforthodontic brackets through ultrasonic devices of themagneto-restrictive type. However, such devices are not very efficientas they require the application of the ultrasonic tool for time periodsupwards of 30 to 40 seconds per bracket. This is a substantial amount oftime for the orthodontist to remove a bracket and generally results insubstantial patient trauma and discomfort.

The present invention provides an improved orthodontic tool and methodfor fracturing the bond between two dental structures that is quick anddoes not cause any significant trauma to the patient. The tool andmethod are also useful for removing adhesive from tooth enamel,polishing the enamel and cleaning the sub-gingiva.

SUMMARY OF THE INVENTION

In one aspect of the present invention, there is provided a dental toolfor fracturing the interface between two dental structures that havebeen secured together. The tool includes a generator for providing powerat a predetermined frequency and a converter for producing ahi-directional movement along the axis of the converter at saidpredetermined frequency. A horn having an outer working end is securedto the converter for transferring said bi-directional movement to one ofsaid dental structures so as to fracture the interface between saiddental structures.

In another aspect of the present invention, there is provided a dentaltool for: (1) removing materials such as orthodontic adhesives from thesurface of teeth; (2) providing microscopic cleaning and polishing ofthe enamel surface; and (3) providing sub-gingiva cleaning. The toolincludes a generator for providing power at a predetermined frequencyand a converter for producing bi-directional movement along the axis ofthe converter at said predetermined frequency. A horn is secured to theconverter and has an outer working end for performing theabove-described functions utilizing the bi-directional movement providedby the converter. In one embodiment the working end is in the form of awedge-shaped tip suitable for removing orthodontic adhesives from atooth surface. In an alternative embodiment, the working end is in theform of a substantially flat tip which is utilized in combination with aliquid to provide cavitation for microscopic cleaning and polishing ofthe enamel surface. In another alternative embodiment, the working endis in the form of a pointed or needle shaped tip suitable forsub-gingiva cleaning. In all of the above embodiments, the working endtip may have an orifice for providing irrigation or evacuation.

In another aspect of the present invention, there is provided a methodfor fracturing the interface between two dental structures that havebeen secured together (such as bonded or banded appliances). The methodincludes providing an ultrasonic tool having a generator for providing apredetermined frequency, a converter for producing a hi-directionalmovement along the axis of the converter and a horn having an outerworking end for transferring said bi-directional movement to one of saiddental structures. The method further includes the step of placing theouter working end of the horn at an acute angle with respect to theinterface between said dental structures.

In yet another aspect of the present invention, there are providedmethods for removing materials such as orthodontic adhesives from thesurfaces of teeth; providing microscopic cleaning and polishing of toothenamel surfaces; and providing sub-gingiva cleaning. These methodsinclude providing an ultrasonic tool having a generator for providingpower at a predetermined frequency, a converter for producinghi-directional movement along the axis of the converter, and a hornhaving an outer working end for transferring the bi-directional movementto accomplish the above-described functions.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a dental tool made in accordance withthe present invention;

FIG. 2 is a perspective view of the tip of the ultrasonic tool of FIG. 1shown within line 2--2;

FIG. 3 is a top plan view of the tip of FIG. 2;

FIG. 4 is a side elevational view of the tip of FIG. 2;

FIG. 5 is a front elevational view of the tip of FIG. 2;

FIG. 6 is an enlarged perspective view of an orthodontic bracket securedto a tooth upon which the tool of FIG. 1 is to be used;

FIG. 7 is an enlarged partial side view of the tip area of the tool ofFIG. 1 as applied against an orthodontic bracket which is secured to atooth from which it is to be removed;

FIG. 8 is a view similar to FIG. 7 illustrating the orthodontic bracketremoved from the tooth; and

FIGS. 9A-D are perspective views of alternative embodiments of the tipof FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the figures there is illustrated an ultrasonic dental tool10 made in accordance with the present invention. The tool 10 isdesigned to be electrically connected to an oscillation generator 12 byan appropriate power cable 13 which is used to produce a predeterminedelectrical frequency. The oscillation generator 12 is a conventionalgenerator as is well known in the prior art. Preferably, the generator12 provides an ultrasonic frequency equal to or greater than about 18kHz. In the particular embodiment illustrated the generator 12 is usedto provide a frequency of about 40 kHz.

The dental tool 10 comprises a converter 14 for producing abi-directional movement along the longitudinal axis X--X of theconverter 14 as illustrated by arrows 15. The converter 14 is made of apiezoelectric material such that movement is substantially directionalalong the longitudinal axis X--X of the converter. It is essential touse a converter which provides substantially only bi-directionalmovement to minimize the radial vibration of the tip and thus providesubstantially only bi-directional movement along a X--X axis. For thepurpose of the present invention, a bi-directional movement shall mean aforward and backward motion along a single axis. Preferably, the lateralmovement at the tip is less than about 40 microns during use of thedevice. Magneto-restrictive devices of the prior art, due to the natureof their construction, produce relatively large amounts of radialvibration (often referred to as lateral) which generates heat and doesnot have a positive function in fracturing the interface (the bond)between the tooth and bracket.

A horn 16 has a connecting end 18 which is secured to the converter 14in any conventional manner and an outer working end 20 which is designedto provide physical movement along the X--X axis. In the particularembodiment illustrated horn 16 is secured to converter 14 by externalthreads formed on a projection which is received in a threaded openingin converter 14. Typically the horn 16 is designed to have a shape,configuration and mass so as to provide the desired amount of movementat its outer working end 20. A working tip 22 is secured at the outerworking end 20 of horn 16. In the particular embodiment illustrated, tip22 is secured to horn 16 by external threads 23 provided on the shankportion 25 which mate with internal threads provided in opening 27 inouter working end 20. It is to be understood that tip 22 may be securedto horn 16 in any desired manner appropriate for such devices. The horn16 tapers down to a relatively narrow cylindrical tip having a diameterD of approximately 0.2 inches (5.08 mm). Preferably, the horn 16 is madeof one of the following materials: titanium, aluminum, titanium alloys,or aluminum alloys. In the particular embodiment illustrated, the hornis made of a titanium alloy. However, it is to be understood that thehorn 16 may be made out of any suitable material for use in anultrasonic tool of the present invention.

A hand gripping handle 17 is secured to converter 14 and horn 16,preferably at a nodal point. In the particular embodiment illustratedhandle 17 is an annular sleeve type structure made of aluminum. However,handle 17 may take any desired configuration and be made of any desiredmaterial.

Referring to FIGS. 2-5 the working tip 22 is shown in greater detail.The tip 22 has an engaging surface 24 which is designed to be placedagainst the work piece for transmitting of the ultrasonic displacementto the work piece. In the particular embodiment illustrated, theultrasonic tool is being used to debond an orthodontic bracket 26 from atooth 28 of a patient. Preferably, as illustrated, the working tip 22 isdesigned so as to receive the bracket 26 and minimize the potential forslipping off. In the particular embodiment illustrated, the working tip22 is provided with a pair of spaced projections 30 disposed on twoopposed sides of the engaging surface 24 so as to provide a receivingarea therebetween. Preferably, as illustrated, the projections 30 arespaced apart a distance D1 which is slightly greater than the width W ofthe orthodontic bracket 26 which is to be received therebetween. Thiswill assist in preventing the tool from moving off the orthodonticbracket due to the vibration of the tool. The tool 10 is designed suchthat the amplitude of movement A of the tip 22 at the outer working endof horn 20 is greater than 0.0005" (0.0127 mm). Preferably the amplitudeA of the tip 22 is in the range of 0.001" (0.0254 mm) to approximately0.005" (0.127 mm). The tip 22 is preferably made of a material havinghigh abrasion resistance. The tip 22 can be made of Ti, Al Ti alloys, Alalloys or stainless steels.

Alternatively tip 22 may be coated with a high abrasion resistantmaterial.

In the preferred form of the present invention a tracking system isprovided in the generator to monitor the frequency and load beingapplied to the tip of the ultrasonic tool 10. The tracking systemmonitors the frequency and identifies the load and recalibrates thefrequency of the generator so as to provide a resonance frequency toprovide optimum power to the tip and substantially constant amplitudemovement at the tip 22. This minimizes the possibility of the tip 22simply stopping due to the amount of load being applied by the user.

In order to more fully understand the operation of the device, anexplanation as to its use will now be set forth. In order to remove anorthodontic bracket 26 which is secured to a tooth 28 by an appropriateorthodontic adhesive, the tip 22 of the tool 10 is placed against thebracket 26 as illustrated in FIG. 7. The engaging surface 24 is designedto transfer the ultrasonic energy to one of the dental structures to beseparated and not between the dental structures. The ultrasonic energyis transferred through bracket 26 to the adhesive between the tooth andbracket. It is believed that the adhesive layer due to its relativelylow modulus of elasticity, dampens the ultrasonic waves which generatesheat and assists in debonding the-bracket. Preferably, the tip is placedagainst the occlusal wings 32 (or occlusal side of the bracket 26). Thegenerator 12 is activated by an appropriate switch means (not shown) soas to provide the desired frequency to piezoelectric converter 14. Thisin turn causes the tip 22 to vibrate in a longitudinal direction X--X ata desired amplitude A and frequency. A slight intermittent force isapplied by the user against the bracket 26 until it is removed from thetooth 28. In applying the tip 22 to the work piece (for example,bracket) to be removed it is desirable that the longitudinal axis of thetool 10 be oriented such that the amplitude of movement as expressed bythe longitudinal axis x--x be oriented at an acute angle with respect tothe plane in which the interface between the bracket 26 and tooth 28substantially lies. The placing of the tool at a 90° angle to theinterface is extremely ineffective and would be discomforting to thepatient. The longitudinal axis placed at an angle α less than about 60°and preferably less than 30°. The time typically required is within afew seconds, typically, within about one second. This is a substantialimprovement over prior art magneto-restrictive devices which require upto about 30 to 40 seconds.

A device made in accordance with the present invention was used todebond orthodontic brackets 26 made of a polycrystal alumina or glassmaterial which were secured to a tooth 28 by commercially availableadhesives, such as System 1+ and Challange Adhesives sold by OrmcoCorporation and Concise and Transbond Adhesives sold by Unitek, thebrackets came off within about one to two seconds leaving the adhesiveon the tooth and with no apparent damage to the tooth enamel. Anyremaining adhesive on the tooth can be easily and quickly removed bystandard deburring techniques, or by utilizing an alternative embodimentof the device and method of the present invention, as described below. Aparticularly important feature of the present invention is that thedebonding occurs extremely quick and is not traumatic to the patient.Furthermore, the loads necessary for bracket removal are substantiallyless than those required by typical removal devices.

It is to be understood that various modifications and changes can bemade without departing from the scope of the present invention. Forexample, in the preferred embodiment illustrated, the ultrasonic dentaltool 10 is used to debond orthodontic brackets from teeth, the tool 10may also be used to fracture the interface between two other dentalstructures that have been secured together, for example, an orthodonticband which has been cemented to a tooth. Additionally, the presentinvention can also be used for fracturing other dental structures suchas dental amalgams and fillings that have been secured to teeth, so longas the bond between the two dental structures is weaker than either ofthe components being secured together which is often the case in dentaland orthodontic appliances. For the purposes of the present invention, adental structure shall be considered any component used in the dental ororthodontic field, including, but not limited to: orthodontic brackets,orthodontic bands, implants, crowns, bridges, teeth, fillings, andbones. It is anticipated that the present invention would be useful inthe treatment of ankylosis.

FIGS. 9 A-D show several alternative embodiments of the working tip 22that is shown in FIG. 2, which are designed to be secured at the outerworking end 20 of horn 16. The working tips 22 shown include externalthreads 23 on the shank portion 25 for securement to outer working end20 of horn 16. In the embodiment shown in FIG. 9A, tip 22 has awedge-like shape 100 in which the four faces of the tip converge todefine a working edge 102. Utilizing this working tip in the ultrasonictool of the present invention facilitates the removal of materials suchas orthodontic adhesives from the enamel surface of the teeth byphysically contacting the adhesive or other material with working edge102 of the wedge-shaped tip 100. The bi-directional movement supplied bythe ultrasonic tool removes the adhesive or other foreign material fromthe enamel surface.

FIG. 9B shows an alternative embodiment of working tip 22 which has asubstantially flat working surface 104. In this embodiment, the flatworking tip is used in the ultrasonic tool in conjunction with a liquidto provide cavitation of the liquid, thereby microscopically cleaningand polishing the enamel tooth surface.

FIG. 9C shows another alternative embodiment of the working tip 22 ofthe present invention. In this embodiment, the tip has a pointed orneedle-shaped tip 106. Utilizing working tip 106 with the ultrasonictool of the present invention facilitates cleaning of the sub-gingiva.The needle-shaped tip is designed to impart the bi-directional movementof the tool to otherwise difficult to reach places, including thesub-gingiva. As shown in FIG. 9C, tip 106 may have an orifice 108 toprovide either irrigation or evacuation at the location of the tip, asdesired in the particular procedure being employed. It will beappreciated that the tip 106 shown in FIG. 9C need not have an orifice108. It will further be appreciated that the tip 100 shown in FIG. 9Amay be provided with an irrigation/evacuation orifice at the location ofworking edge 100.

FIG. 9D shows an alternative working tip embodiment generally similar tothat shown in FIG. 9B, with the exception that the tip shown in FIG. 9Dhas an irrigation/evacuation orifice 110 generally in the center of flatworking surface 104. The methods of using the ultrasonic tool of thepresent invention with each of the working tip embodiments shown inFIGS. 9 A-D will now be described.

When the ultrasonic dental tool of the present invention is fitted withworking tip 22 of the type shown in FIG. 9A, the device is most suitablefor removing adhesive or other foreign material from an enamel toothsurface. This is accomplished by placing the working edge 102 of tip 22directly in contact with the foreign material (adhesive) to be removedsuch that the bi-directional movement supplied by the device loosens andremoves the adhesive from the tooth surface. To accomplish this adhesiveremoval, it is preferable that the ultrasonic device is disposed at anangle of less than about 60° with respect to the plane of the toothsurface having the adhesive thereon. Furthermore, the device ispreferably operated at a frequency in the range of about 20 to 60 kHz.

When the ultrasonic dental tool of the present invention is fitted witha working tip 22 of the type shown in FIG. 9B or D, the device iscapable of providing microscopic cleaning and polishing of the enameltooth surface. This is accomplished by first providing a liquid layeradjacent the tooth surface and orienting the dental tool so that theflat working surface 104 is parallel to the tooth surface being cleanedor polished. There may be a space between the working surface 104 andthe enamel surface, which may vary from direct contact (0 mm) to a fewmillimeters (on the order of about 0.1-10 mm). The liquid layer may bemaintained between the tooth surface and flat working surface 104, asfor example by dispensing the liquid through orifice 110 shown in FIG.9D. The bi-directional movement of the flat working surface 104 causescavitation of the liquid which in turn provides the cleaning andpolishing action on the enamel surface. Suitable liquids for use in thismethod are water, saline, or slurries containing suitable abrasiveparticles such as pumice or silica. Furthermore, the liquid may comprisedisinfectants, antiseptic and other medicated solutions. The desiredfrequency of oscillation of working surface 104 to induce cavitation inthe liquid is preferably in the range of about 20 to 60 kHz.

The working tip embodiment shown in FIG. 9C is used in the ultrasonicdental tool of the present invention to provide sub-gingiva cleaning.This particular embodiment is most suitable for sub-gingiva cleaningsince the pointed or needle-shaped tip 106 is capable of reachingotherwise difficult to reach locations. To accomplish this, the tip 106is placed in contact with a tooth in the sub-gingiva region, whereby thebi-directional movement provided by the device cleans that region.

It is to be understood that various other changes and modifications maybe made without departing from the scope of the present invention. Forexample, a separate tip may be eliminated and the outer working end ofthe horn may be in the form of any one of the embodiments described, toaccomplish the desired result. The present invention being limited bythe following claims.

What is claimed is:
 1. A method for removing adhesive from the surfaceof a tooth, comprising the steps of:providing an ultrasonic devicehaving a converter for producing a substantially bi-directional movementalong the axis of the converter at a predetermined frequency, a hornhaving a connecting end and an outer working end, said connecting endbeing secured to said converter, for transferring said bi-directionalmovement to said outer working end of said horn, said outer working endbeing substantially wedge-shaped to provide a chiseling effect;activating said device such that said bi-directional movement of saidouter working end has an amplitude in the range of 0.0005"-0.005"; andplacing the outer working end of said horn in contact with the adhesive,whereby the adhesive is removed from tooth surface by said chiselingeffect.
 2. A method according to claim 1 wherein the ultrasonic deviceis disposed at an angle less than about 60° with respect to the plane ofthe tooth surface having the adhesive thereon.
 3. A method according toclaim 2 wherein the ultrasonic device is operated at a frequency in therange of about 20 to 60 kHz.